1. Field of the Invention
Embodiments of the present invention generally relate to a method and apparatus for hydroprocessing of hydrocarbon materials into clean volatile liquid products.
2. Description of the Related Art
Most hydroprocessing and other direct liquefaction processes for low-volatile hydrocarbon materials (LVHMat), such as insufficiently hydrogenated carbonaceous materials including as coal, heavy petroleum feedstock, tar-sand oil, shale oil or any process derived carbonaceous products, are based on catalytic hydroconversion of an LVHMat oil slurry in multi-stage ebullated bed reactors using catalyst extrudates or slurry bed reactors using fine dispersed catalysts. Depending upon the feed, LVHMat's properties and operating conditions, less than 70 w % of distillate oils can be recovered.
Because of exothermic reactions in the LVHMat hydroprocess, prior processes typically utilized a bubble-column reactor system. Conventional bubble column, slurry bed and fluid bed reactors currently used for LVHMat hydroprocessing are nearly fully mixed; resulting in moderate conversion since the fresh unreacted feed and fully reacted material both have a good chance of leaving the reactor. Also these reactor systems do not have sufficient turbulence to allow proper mass and heat transfer, resulting in under-reaction or over-reaction for the desired products.
The organic fraction of LVHMat is composed of a wide range of organic compound types, varying both in their molecular configuration and their degree of reactivity. As a result, some of the organic compounds react early in the process, yielding desirable light products, and some compounds react at the later part of the process. Current processes require overall reaction times of 15 to 90 minutes. Unless the reaction products formed in the early part of the process are removed, they start to retrogress. This happens in the form of further cracking r, ultimately to light hydrocarbon gases. Another retrogression route for both the light and the heavy product compounds is through polymerization to refractory high molecular weight aromatics or tars.
To address these problems in LVHMat hydroprocessing and other liquefaction processes, Simpson in U.S. Pat. No. 6,054,043 (“Simpson”) disclosed a system including several fluid bed reactors and a single stage plug-flow reactor operating in the turbulent flow region with staged venting of volatile products followed by several fluid bed reactors with optional injection of supplemental hydrogen gas, catalyst, or fresh solvent. Simpson has also disclosed improvements providing an adequate presence of active hydrogen, adequate agitation to overcome mass transfer limitation, and a high rate of heat transfer.